Note that our microbiome is still not well understood. We need to learn more:

James Greenblatt’s provocative idea — that psychiatric woes can be solved by targeting the digestive system — is increasingly reinforced by cutting-edge science. For decades, researchers have known of the connection between the brain and the gut. Anxiety often causes nausea and diarrhea, and depression can change appetite. The connection may have been established, but scientists thought communication was one way: it traveled from the brain to the gut, and not the other way around.

But now, a new understanding of the trillions of microbes living in our guts reveals that this communication process is more like a multi-lane superhighway than a one-way street. By showing that changing bacteria in the gut can change behavior, this new research might one day transform the way we understand — and treat — a variety of mental health disorders.

For Greenblatt, this radical treatment protocol has actually been decades in the making. Even during his psychiatric residency at George Washington University, he was perplexed by the way mental disorders were treated. It was as if, he said, the brain was totally separate from the body. More than 20 years of work treating eating disorders emphasized Greenblatt’s hunch: that the connection between body and mind was more important than conventional psychiatry assumed. “Each year, I get more and more impressed at how important the GI tract is for healthy mood and the controlling of behavior,” Greenblatt said. Among eating disorder patients, Greenblatt found that more than half of psychiatric complaints were associated with problems in the gut — and in some patients, he says he has remedied both using solely high-dose probiotics, along with normalizing eating.

Greenblatt’s solution might strike us as simple, but he’s actually targeting a vast, complex, and mysterious realm of the human body: around 90 percent of our cells are actually bacterial, and bacterial genes outnumber human genes by a factor of 99 to 1. But those bacteria, most of which perform helpful functions, weren’t always with us: a baby is essentially sterile until it enters the birth canal, at which point the bacteria start to arrive — and they don’t stop. From a mother’s vaginal microbes to hugs and kisses from relatives, the exposures of newborns and toddlers in their earliest years is critical to the development of a robust microbiome.

While researchers have established a compelling link between gut bacteria and mental health, they’re still trying to figure out the extent to which the human microbiome — once it’s populated in early childhood — can be transformed. “The brain seems to be hardwired for anxiety by puberty and early adolescence,” Foster said. If the microbiome is part of that hardwiring, then it would suggest that once we pass a certain threshold, the impact of bacterial tweaks on problems like depression and anxiety might wane.

In one Japanese study, for instance, researchers were only able to change the baseline stress characteristics of germ-free mice until nine weeks of age. After that, no variety of bacterial additions to the mice’s guts could properly regulate stress and anxiety levels. The explanation for this phenomenon might lie in what’s known as “developmental programming” — the idea that various environmental factors, to which we’re exposed early on, greatly determine the structure and function of organs including the gut and the brain.

“There are changes that happen early in life that we can’t reverse,” said John Cryan, a neuroscientist at the University of Cork in Ireland and a main investigator at the Alimentary Pharmabiotic Centre. “But there are some changes that we can reverse. It tells us that there is a window when microbes are having their main effects and, until this closes, many changes can be reversed.”

Even if our gut bacteria carries the biggest influence when we’re young, experts like Greenblatt and Cryan are still convinced that tweaking these bacteria later in life can yield profound behavioral and psychological changes. In a study led by Cryan, anxious mice dosed with the probiotic bacterium Lactobacillus rhamnosus (JB-1) showed lower levels of anxiety, decreased stress hormones, and even an increase in brain receptors for a neurotransmitter that’s vital in curbing worry, anxiety, and fear.

John Bienenstock, a co-author on that study, compared the probiotics’ effects to benzodiazepines like Valium and Xanax. “The similarity is intriguing. It doesn’t prove they both use the same pathway [in the brain], but it’s a possibility.”

That's one problem w lab experiments--by their very nature of design--they exclude investigation of complexity dependent upon the very nature of complex, surrounding environments, which...uh oh...are necessary to sustain and transform biomes in our complex internal environments (of which some remain external to us, digestive track, skin, hair, etc). There is no one biome nor one vector to create and influence a biome...

Sometimes really smart people and scientists are simply made to reason like dipshits... because that's their environment: we teach and pay for science to be an incrementalist profession of narrow specialization and blind inquiry.

The difficulty of understanding is not the issue. And it's not what I was railing against... it was this,

"“There are changes that happen early in life that we can’t reverse,” said John Cryan, a neuroscientist at the University of Cork in Ireland and a main investigator at the Alimentary Pharmabiotic Centre."

A better way to inspire honesty would have been to suggest, “There are changes that happen early in life that we can’t reverse--YET” or even better, "There appear to be changes that happen early in life that we don't yet know if they can be reversed and if so, how to do that".

This surmise will enter into the public record and some PhD student will turn it into a thesis... or layperson quote a PubMed... and dipshits.

It’s a distinct possibility: in one 2013 proof-of-concept study, researchers at UCLA showed that healthy women who consumed a drink with four added probiotic strains twice daily for four weeks showed significantly altered brain functioning on an fMRI brain scan. The women’s brains were scanned while they looked at photos of angry or sad faces, and then asked to match those with other faces showing similar emotions.

Those who had consumed the probiotic drink showed significantly lower brain activity in the neural networks that help drive responses to sensory and emotional behavior. The research is “groundbreaking,” Cryan said, because it’s the first trial to show that probiotics could affect the functioning of the human brain. Still, he notes that the results need to be interpreted with care.